The role of sodium bicarbonate in the sporocidal effect of glutaraldehyde

Glutaraldehyde is a useful cold sterilant to prevent the spread of infective disease. It is not only an effective disinfectant but also a powerful sporicide. Its sporicidal activity, however, is more effective in an alkaline environment which can be achieved by adding 0.3% (W/V) sodium bicarbonate. This phenonmenon indicates that sodium bicarbonate plays an important role in the sporicidal process although different opinions have been raised. In this presentation, the interfering mechanism of sodium bicarbonate on spore germination of both Bacillus stearothermophilus and Bacillus subtilis was reviewed and explored step-by-step. Fourier transform infrared (FTIR) spectroscopic studies suggested that some protein components on the spores has been altered after the alkaline treatment. When these spores were subjected to altomic force microscopic analysis, it revealed significant changes on the spore surface similar to the morphological appearance of the extreme dormant spores prepared from sulfur limiting culture. Both electron microscopic examinations of the spores and proteomic analysis of the spore components implied that demolition of the small molecular weight proteins in the outer coat layer had taken place and it was properly responsible for the dormancy induced. Our results, thus, demonstrate that certain small molecular weight proteins in the spore coat layers were demolished in the presence of sodium bicarbonate followed by the permanent fixation of spore structure by glutaraldehyde.